Longest-running material creep test

The longest-running material creep test lasted for 14,868 days (356,838 hours) and was achieved by National Institute for Material Science (Japan) in Meguro, Tokyo, Japan, on 14 March 2011.

The term "creep" describes a form of deformation experienced by materials when placed under consistent strain at high temperatures. Under these conditions, metals will stretch slowly, even if the load placed on them is below the level where any deformation would be expected under typical conditions. Creep can be described as occurring in three stages: primary creep, where the material deforms at a high rate for a short time; secondary creep, where the material deforms at a low but uniform rate for a long time; and finally tertiary creep, during which stage the material begins to fracture and break apart.

The record creep test is the continuous measurement of creep deformation of steel, and it had begun on 19th June 1969, under the condition of constant temperature of 400 degrees Celsius and a constant tensile load with an initial stress of 294 MPa. The specimen was a cylindrical shape with a 10 mm diameter and 50 mm gauge length. The measurement had continued until 2011 with only one interruption (9th February, 1974 - 12th February 1975) due to the replace of the facilities. The test was performed to the JSA test standard JIS Z 2271.

In comparison, the second longest known creep test was by the German company Siemens, which was discontinued in 2000. The test duration was 356,463 hours, which is equivalent to 14,852 days and 15 hours.

Such tests can be used to determine how material will deform in a given period, or how long it will endure before entering the tertiary stage. Knowledge of these characteristics is vital for the manufacture of things such as jet engines or turbines, when the failure of internal components operating under extreme conditions can result in the loss of life or injury.